The present invention relates to coupling out light e.g. from a laser cavity.
Today, most DWDM component test systems for high dynamic range are based on a tunable laser source (TLS) that uses a low source spontaneous emission (SSE) optical output. A laser beam may have an improved signal to noise ratio (SNR), if it is coupled out just behind a wavelength selective device as disclosed e.g. in EP-A-921614. Such output shall be referred to the following as “Low-SSE output”.
U.S. Pat. Nos. 5,812,567, 5,499,134, and 5,511,086 (Su) disclose various optical arrangements for decoupling light. In particular, Su provides a polarization dependent beam splitter receiving light beams from different directions and with different and defined states of polarization. While the arrangement of Su requires to already receive adequately polarized light, EP-A-1172906 discloses an optical arrangement for direction dependent coupling out of light, wherein polarization converters are provided for actively converting the states of polarization in order to adjust out-coupling ratios for the light beams propagating in different directions. The teaching of EP-A-1172906 (by the same inventor and the same applicant) is incorporated herein by reference as well as by claiming its priority.